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e0537c9f82
Under heavy write load, we've seen the cl_tasks list grows to millions of entries. Even though the list is extremely long, the system still runs fine until the user wants to get the information of all active RPC tasks by doing: When this happens, tasks_start acquires the cl_lock to walk the cl_tasks list, returning one entry at a time to the caller. The cl_lock is held until all tasks on this list have been processed. While the cl_lock is held, completed RPC tasks have to spin wait in rpc_task_release_client for the cl_lock. If there are millions of entries in the cl_tasks list it will take a long time before tasks_stop is called and the cl_lock is released. The spin wait tasks can use up all the available CPUs in the system, preventing other jobs to run, this causes the system to temporarily lock up. This patch fixes this problem by delaying inserting the RPC task on the cl_tasks list until the RPC call slot is reserved. This limits the length of the cl_tasks to the number of call slots available in the system. Signed-off-by: Dai Ngo <dai.ngo@oracle.com> Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.